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| United States Patent |
5,674,628
|
|
Hargis
, et al.
|
October 7, 1997
|
Solventless butadiene- vinylidene chloride adhesives containing
macromonomers for the bonding of rubber to metal
Abstract
Disclosed is a water-based adhesive with enhanced effectiveness for bonding
metal and rubber substrates for uses such as vibration damping devices.
The adhesive is formulated from a latex which includes at least one
conjugated diene and a macromonomer containing at least two ethylene oxide
repeat units.
| Inventors:
|
Hargis; I. Glen (Tallmadge, OH);
Kovalchin; John P. (Akron, OH);
Sharma; Satish C. (Stow, OH);
Weinert; Raymond J. (Macedonia, OH);
Wilson; John A. (Arkon, OH)
|
| Assignee:
|
GenCorp Inc. (Fairlawn, OH)
|
| Appl. No.:
|
649744 |
| Filed:
|
May 15, 1996 |
| Current U.S. Class: |
428/462; 156/327; 428/495; 428/625; 524/432 |
| Intern'l Class: |
B32B 015/06; C09J 109/00; C09J 127/16 |
| Field of Search: |
428/462,495,625,626
156/327
523/202
|
References Cited
U.S. Patent Documents
| 4119587 | Oct., 1978 | Jazenski et al. | 524/148.
|
| 4483962 | Nov., 1984 | Sadowski | 524/552.
|
| 4740546 | Apr., 1988 | Masuda et al. | 524/568.
|
| 4988753 | Jan., 1991 | Rullmann et al. | 524/555.
|
| 4994519 | Feb., 1991 | Scheer | 524/519.
|
| 5036122 | Jul., 1991 | Auerbach et al. | 524/430.
|
| 5178675 | Jan., 1993 | Sexsmith | 106/13.
|
| 5200455 | Apr., 1993 | Warren | 524/430.
|
| 5200459 | Apr., 1993 | Weih et al. | 524/459.
|
| 5281638 | Jan., 1994 | Mowrey | 524/105.
|
| 5300555 | Apr., 1994 | Weih et al. | 524/571.
|
| 5330844 | Jul., 1994 | Taguchi et al. | 523/202.
|
| 5478654 | Dec., 1995 | Hargis et al. | 428/462.
|
| Foreign Patent Documents |
| 0 266 879 A1 | May., 1988 | EP.
| |
| 0 287 190 A3 | Oct., 1988 | EP.
| |
| 0 516 360 A1 | Dec., 1992 | EP.
| |
| 2 223 019 | Mar., 1990 | GB.
| |
| WO93/12189 | Jun., 1993 | WO.
| |
Primary Examiner: Yoon; Tae
Attorney, Agent or Firm: Rywalski; Robert F., Laferty; Samuel B.
Parent Case Text
CROSS-REFERENCE
This is a division of application Ser. No. 08/440,586 filed May 15, 1995
U.S. Pat. No. 5,589,532 of I. Glen Hargis et al., for "SOLVENT-LESS
BUTADIENE-VINYLIDENE CHLORIDE ADHESIVES CONTAINING MACROMONOMERS FOR THE
BONDING OF RUBBER TO METAL."
Claims
What is claimed is:
1. In a laminate, including:
a) a rubber substrate comprising natural rubber, or a synthetic rubber
having at least 30 weight percent repeat units from at least one
conjugated diene having from 4 to 12 carbon atoms, or combinations
thereof;
b) a metal substrate, and
c) an adhesive layer which adheres said metal substrate to said rubber
substrate, wherein said adhesive layer is a cured reaction product of an
adhesive composition comprising a latex and a nitrosamine crosslinking
agent or its precursors;
the improvement wherein said latex is the emulsion polymerization product
from unsaturated monomers, said unsaturated monomers comprising;
1) an ethylene oxide macromonomer comprising an unsaturated terminal group
and from 2 to 40 ethylene oxide repeat units, and
2) at least one conjugated diene having from 4 to 12 carbon atoms.
2. A laminate according to claim 1 wherein said ethylene oxide macromonomer
is from about 0.5 to about 20 weight percent and said at least one
conjugated diene is at least 30 weight percent of said unsaturated
monomers.
3. A laminate according to claim 2, wherein said unsaturated monomers
further comprise at least 5 weight percent vinylidene chloride.
4. A laminate according to claim 2, wherein said adhesive composition
further includes a bismaleimide compound and zinc oxide.
5. A laminate according to claim 3, wherein said adhesive composition
further includes a bismaleimide compound and zinc oxide.
6. A laminate according to claim 3, wherein said ethylene oxide
macromonomer is from about 1 to about 10 weight percent of said
unsaturated monomers.
7. A laminate according to claim 6, wherein said unsaturated terminal group
of said ethylene oxide macromonomer is an ethylenically unsaturated
terminal group.
8. A laminate according to claim 6, wherein said unsaturated terminal group
of said ethylene oxide macromonomer is a vinyl aromatic group or an
acrylic group.
9. A process for improving the bonding of an adhesive, said process
comprising the sequential steps of
a) applying at least one layer of an adhesive to at least a portion of a
metal substrate, or a rubber substrate, or both to form at least one
adhesive layer and allowing at least a portion of the water in said
adhesive layer to evaporate,
b) adhering said metal substrate to said rubber substrate with said
adhesive layer between said metal substrate and said rubber substrate, and
c) subsequently heating the adhesive layer to cure and form a bond between
the metal substrate and the rubber substrate wherein said adhesive
comprises a latex produced by emulsion polymerization of unsaturated
monomers and a nitrosamine crosslinking agent or its precursors, said
unsaturated monomers comprising:
1) an ethylene oxide monomer comprising an unsaturated terminal group and
from 2 to 40 ethylene oxide repeat units and
2) at least one conjugated diene having from 4 to 12 carbon atoms.
10. A process according to claim 9, wherein the ethylene oxide macromonomer
is present as repeat units at concentrations from 0.5 to 20 weight percent
of the total repeat units in said latex, said at least one conjugated
diene is present as repeat units at concentrations of at least 30 weight
percent in said latex and said latex further comprises at least 5 weight
percent repeat units from vinylidene chloride.
Description
FIELD OF THE INVENTION
The invention relates to a composition for bonding natural and synthetic
elastomers to metallic substrates under vulcanizing conditions, which
composition comprises an aqueous dispersion, containing an aromatic
nitroso compound, a latex which includes an ethylene oxide macromonomer,
and optionally conventional adhesion promoters, metal oxides, dispersion
aids, fillers and processing aids.
BACKGROUND OF THE INVENTION
U.S. Pat. No. 4,988,753 relates to an adhesive from a mixture of vinyl
chloride/vinylidene chloride/acrylic acid and polyethylene.
U.S. Pat. No. 5,036,122 teaches adhesive compositions for bonding metals to
rubbers based generally on polybutadiene latex having at least one halogen
from the group of chlorine, bromine, or iodine. The composition further
comprises a poly-C-nitroso compound and a polymaleimide.
U.S. Pat. No. 5,200,459 teaches a poly(butadiene) latex prepared by
emulsion polymerization in the presence of polyvinyl alcohol and a
stabilizing solvent.
U.S. Pat. No. 5,281,638 relates to a water based adhesive having
chlorosulfonated polyethylene latex as a film forming polymer.
The purpose of this invention is to create an improved water-based adhesive
and a process using said adhesive to bond metal to rubber.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an improved aqueous
bonding composition which has universal utility for adhesively bonding
substrates such as rubber and metals. It avoids the disadvantages of
solvent based adhesives e.g., flammability and the release of volatile
organics during drying and curing. A macromonomer of polyethylene oxide
present in the latex improves adhesive bonding. A copolymer comprising
butadiene and vinylidene chloride has shown particular desirability as the
copolymer of the latex.
DESCRIPTION OF THE INVENTION
A bonding composition for bonding natural and/or synthetic elastomers to
metallic substrates under vulcanizing conditions, comprises an aqueous
dispersion, which contains a polymer from a ethylene oxide macromonomer
and at least one conjugated diene as a polymeric film-forming substance,
an aromatic nitroso compound crosslinking agent and optionally a
coactivator, conventional adhesion promoters, metal oxide, fillers,
dispersion aids and processing aids.
The polymeric film-forming substance used in the bonding composition in
accordance with the invention results in a higher bond strength between
the natural and/or synthetic elastomer (rubber) and the metal substrate.
An organic primer layer on said metal substrate is not needed for good
adhesion.
In bond deformation tests, e.g. between rubber and metal, using a peel
deformation, the failure occurs within the rubber substrate in most cases
indicating that the adhesive layer and bond are stronger than the rubber
and resulting in rubber being retained on the metal surface.
The ethylene oxide macromonomer desirably has a molecular weight above 200
and more desirably above 300 and comprises at least one reactive
unsaturated terminal group and at least 2, more desirably at least 3
repeat units from ethylene oxide. The term macro-monomer is used to define
a monomer that includes within it a macromolecule such as an oligomer or
polymer. Desirably the macromonomer has a number average of from 2 to 40
ethylene oxide repeat units and more desirably from 2 to 15 repeat units.
The at least one reactive unsaturated terminal group includes a carbon to
carbon double bond that is copolymerizable with the monomers of the latex.
A preferred reactive unsaturated terminal group is derived from TMI.TM.
(m-isopropenyl-.alpha.-.alpha.-dimethyl benzyl isocyanate). Reactive
unsaturated terminal groups include vinyl, vinyl aromatic (includes
TMI.TM.), (alkyl)acrylic, allylic, and acrylic having from 3 to 20 carbon
atoms more desirably from 3 to 12 carbon atoms. TMI.TM. is preferred due
to its ease of incorporation into the macromonomer. The ethylene oxide
repeat units can be present as a homooligomer or homopolymer; a block
copolymer with other polyethers; random polyether copolymer wherein the
polyether may include as repeat units other ether repeat units having 2 to
10 carbon atoms. The macromonomer may have two or more terminal groups.
Preferably only one terminal group is unsaturated. The other terminal
group or groups are desirably not unsaturated nor chemically reactive in
the free radical emulsion polymerization of the latex. The examples show
nonreactive groups such as octylphenoxy and nonylphenoxy. These
nonreactive groups are initiator fragments from forming the polyether.
Other initiator fragments may form the one or more nonreactive terminal
groups.
The ethylene oxide macromonomers are desirably formed from a hydroxyl
terminated oligomer or polymer having said at least 2 or at least 3
ethylene oxide repeat units which is reacted with an unsaturated compound
having a group reactive by condensation mechanisms with the hydroxyl group
of the oligomer or polymer. The hydroxyl terminated oligomers or polymers
are commonly commercially available as emulsifiers which are made by the
polymerization of cyclic ethers. The polymerization initiator or the
terminating agent of polymerization can be chosen or controlled to result
in one or more terminal hydroxyl groups and as many unreactive terminal
groups as desired.
Unsaturated compounds having groups reactive with hydroxyl groups include
TMI.TM. (m-isopropenyl-.alpha.-.alpha.-dimethyl benzyl isocyanate),
isocyanatoethyl methacrylate and other isocyanates having unsaturation
also having from 3 to 20 carbon atoms, epoxy acrylates and methacrylates
having from 5 to 20 carbon atoms, acrylic acids and alkyl derivatives
thereof having from 3 to 20 carbon atoms, and dicarboxylic acids or their
anhydrides having from 4 to 20 carbon atoms.
Also contemplated is where a hydroxyl or amine terminated oligomer having 2
or more ethylene oxide repeat units is reacted with a diisocyanate having
from 3 to 25 carbon atoms forming an isocyanate terminated oligomer with 2
or more ethylene oxide repeat units. That isocyanate terminated oligomer
can then be reacted with hydroxyalkyl esters of (alkyl)acrylic acids
having from 5 to 15 carbon atoms to form macromonomers. Alternatively the
hydroxy alkyl esters of alkyl(acrylic acids), such as
2-hydroxyethylacrylate, may be reacted first with the diisocyanate and
that reaction product reacted with the hydroxyl or amine terminated
oligomer with 2 or more ethylene oxide repeat units to form a
macromonomer.
Isocyanate groups react with hydroxyls to form urethane linkages, epoxy
groups react with hydroxyls to form ether linkages, and carboxylic acid
groups react with hydroxyls to form ester linkages. When bonds are formed
by an esterification condensation mechanism the use of catalysts (e.g.
triphenylphosphonium bromide and tetrabutyltitanate), higher temperatures
(e.g. from about 50.degree. to about 150.degree. C.) or the removal of
esterification by-products may increase reaction rates or yields.
When forming the macromonomers from hydroxyl group containing monomers,
desirably the hydroxyl groups are present in equivalent amounts to the
groups reactive with them but either reactant may be present in excess
because some macromonomer is still formed. It is preferable to have excess
hydroxyl groups rather than excess of the unsaturated compounds having
groups reactive with the hydroxyl groups. Desirable ratios of the reactive
groups are from about 0.5:1 to about 1.5:1 and more desirably from about
0.9:1 to about 1:0.9.
The ethylene oxide macromonomers are desirably used in the latex in amounts
from about 0.5 to about 20 wt. % based on the total of all monomers in the
latex, more desirably from about 0.7 to about 15 wt. %, and preferably
from about 1 to about 10 wt. %. These amounts may also be expressed as wt.
% of repeat units from these macromonomers in the final latex.
The ethylene oxide macromonomers appear to result in enhanced adhesion of
the adhesive to both the metal and rubber substrates. These adhesives
perform significantly better because the ethylene oxide repeat units are
in a macromonomer form that can copolymerize with the diene monomers used
to form the latex. In most adhesive applications wetting is an essential
step in forming a bond. After wetting occurs at the interface then
interdiffusion or interaction of the materials to form a bond can occur.
Facilitating wetting usually results in better bond strength.
The remainder of the latex is formed from common emulsion polymerized
monomers. These monomers generally have molecular weights much lower than
the at least 200 or 300 molecular weight anticipated for the macromonomer.
In that the macromonomer does copolymerize it may be considered as a
monomer. Desirably at least 30 wt. % of the monomers are at least one
conjugated diene monomer having from 4 to 12 carbon atoms. More desirably
the at least one conjugated diene monomer is from about 30 to about 99.5
wt. %, preferably from about 40 to about 95 wt. %, and most preferably
from about 50 to about 94 wt. % of the total monomers in the latex. The
diene repeat units are postulated to improve wetting and interpenetration
of the adhesive with the rubber substrate.
Desirably the latex monomers include at least 5 wt. %, and more desirably
from about 5 to about 60 wt. % of vinylidene chloride based on all the
monomers of the latex. The vinylidene chloride being more polar than the
conjugated dienes is believed to enhance wetting and adhesion to the metal
substrate. Additional monomers of vinyl aromatics having from 6 to 12
carbon atoms, and ethylenically unsaturated monomers having one or more
heteroatoms of oxygen and/or nitrogen and from 3 to 12 carbon atoms may be
present in the latex in small amounts such as desirably less than about
10, 15, or 20 wt. % based on the total monomers. Such monomers are shown
in the seed latex in the example (styrene and itaconic acid). Incorporated
by reference are U.S. Pat. Nos. 4,483,962 and 5,200,459 for their
teachings of other monomers that can be included in latex polymers. The
above recited monomer percentages may be expressed as percentages of
repeat units from these monomers in the final latex.
The latex can be made from a seeded polymerization where the seed latex is
formed first and then swollen with additional monomers which are
polymerized into the final latex. Although the latex can be any solids
content achievable without coagulation the commercially desirable
concentrations are from about 30 to 60 wt. % solids. Emulsifiers are used
in the polymerization to stabilize the particles against coagulation.
Their amount and specific type may vary within ranges well known to the
art. Initiators are used to initiate the polymerization of monomers to
polymers. The specific initiators chosen and the amounts thereof depend on
the polymerization temperature chosen.
The poly-carbon-nitroso compound (nitrosamine crosslinking agent) functions
to chemically crosslink the latex polymer with itself and to the rubber
during the bonding process. The nitroso compound may be replaced with the
corresponding oxime or corresponding nitro compound with the appropriate
oxidation/reduction agent (vulcanization accelerators serve as oxidants
and barium oxide is an effective reducing agent). Suitable nitroso
compounds include poly(p-dinitrosobenzene) and other compounds having one
or more aromatic nuclei (such as benzene, naphthalenes, anthracenes,
biphenyl and the like), to which two or more nitroso groups are bonded to
non-adjacent ring carbon atoms.
The nuclear hydrogen atoms of the aromatic nucleus can be replaced by
alkyl, alkoxy, cycloalkyl, aryl, aralkyl, alkaryl, arylamine, arylnitroso,
amino, halogen, and like groups. The presence of such substituents on the
aromatic nuclei has little effect on the activity of the nitroso compounds
in the present invention. As far as is presently known, there is no
limitation as to the character of the substituent, and such substituents
can be organic or inorganic in nature. Thus, where reference is made
herein to a nitroso compound, it will be understood to include both
substituted and unsubstituted nitroso compounds, unless otherwise
specified.
Particularly preferred nitroso compounds are characterized by the formula:
(R).sub.m --Ar--(NO).sub.2
wherein Ar is selected from the group consisting of phenylene and
naphthalene; R is a monovalent organic radical selected from the group
consisting of alkyl, cycloalkyl, aryl, aralkyl, alkaryl, arylamine, and
alkoxy radicals having from 1 to 20 carbon atoms, amino, or halogen, and
is preferably an alkyl group having from 1 to 8 carbon atoms; and m is
zero, 1, 2, 3, and 4, and preferably is zero.
Examples of suitable compounds are : m-dinitrosobenzene,
p-dinitrosobenzene, m-dinitrosonaphthalene, p-dinitrosonaphthalene,
2,5-dinitroso-p-cymene, 2-methyl-1,4-dinitrosobenzene,
2-methyl-5-chloro-1,4-dinitrosobenzene, 2-fluoro-1,4-dinitrosobenzene,
2-methoxy-1,3-dinitrosobenzene, 5-chloro-1,3-dinitrosobenzene,
2-methoxy-1,3-dinitrosobenzene, 2-benzyl-1,4-dinitrosobenzene and
2-cyclo-hexyl-1,4-dinitrosobenzene.
The use of poly(p-dinitrosobenzene) (PDNB) or
poly(1,4-dinitrosonaphthalene) is preferred in bonding composition in
accordance with the invention. The desired amounts of the nitroso amine
crosslinking agent is from about 50 to about 150 parts on a dry wt. basis
per 100 parts of the latex on a dry wt. basis. PDNB was used in the
examples as a 50% dispersion in water.
The adhesive desirably includes a co-activator for cure such as a
polymaleimide compound. The polymaleimide compound may be an aliphatic or
aromatic polymaleimide and must contain at least two maleimide groups.
Aromatic polymaleimides having from about 2 to 100 aromatic nuclei wherein
no more than one maleimide group is directly attached to each adjacent
aromatic ring are preferred. Particularly preferred aromatic polymaleimide
compounds have the formula:
##STR1##
wherein x is from about 0 to 100. Such polymaleimides are common materials
of commerce and are sold under different trade names by different
companies, such as BMI-M-20 and BMI-S polymaleimides supplied by Mitsui
Toatsu Fine Chemicals, Incorporated.
These co-activators are used to improve the crosslinking of the latex
polymer and result in higher bond strength between the latex polymer and
the rubber substrate. A preferred compound is
1,1-(methylenedi-4-1-phenylene bismaleimide. The co-activator is desirably
used in amounts from 0 to 200 parts by weight (dry basis) per 100 parts by
weight (dry basis) of the latex. U.S. Pat. No. 5,036,122 is hereby
incorporated by reference for its teachings on nitroso crosslinking agents
and co-activators.
The bonding composition in accordance with the invention, may also contain
conventional additives such as organo silanes, dispersing agents, adhesion
promoting resins such as phenol formaldehyde, carbon black, silica,
calcium carbonate, oxides of the metals Al, Ca, Zn, Mg, Pb, Zr, also
zirconium salts, e.g. zirconium aluminate, and lead salts of inorganic
and/or organic acids, e.g. basic lead carbonate.
Dispersing agents are used to form stable dispersions from the particulate
components. They include addition products of alkylphenols, such as
nonylphenol, and ethylene oxide, fatty alcohol or a fatty alcohol partial
ester of phosphoric acid. The dispersion may additionally be stabilized
with polyvinylalcohol or Polywet.TM. such as Polywet Z-1766 a sodium salt
of a polyfunctional oligomer or water-soluble colloids, such as
methylcellulose, methylhydroxylpropylcellulose or hydroxyethylcellulose.
As previously recited the use of poly (vinyl alcohol) is discouraged in
these formulations.
It is desirable to add small amounts of benzoquinone to inhibit premature
crosslinking or gelling of the adhesive. The benzoquinone or an equivalent
thereto is desirably used in amounts from about 0.05 to about 1.5 parts by
weight and preferably from about 0.1 to about 1.0 parts by weight based on
100 parts by weight to the latex on a dry basis.
Organic solvents and/or coalescing solvents may be used in minor amounts in
the adhesive, which should not exceed 5, 10, or 15 weight percent and are
desirably not present. Organic solvents which are included in these weight
percents are those that volatilize in 1 hour at 150.degree. C. at
atmospheric pressure.
The adhesive composition in accordance with the invention may be used to
bond natural rubber, synthetic rubber or combinations thereof (also known
as elastomers) to a metal substrate under vulcanizing conditions. The
rubber may be in either the crosslinked or non-crosslinked form. Examples
of synthetic rubbers include polychloroprene rubber, styrene-butadiene
rubber, butadiene rubber, polyisoprene, poly(octenamer), nitrile rubber,
rubber comprising an ethylene-propylene copolymer or an
ethylene-propylene-diene terpolymer. The rubber is mixed with fillers,
oils, curatives etc. as is well known to the art. Table IX shows a
formulation used for testing purposes. The rubber substrate may be used as
a crosslinked shaped article or as an uncured composition that is shaped
and crosslinked contemporaneously with the adhesive bonding.
The substrate may consist of metallic materials, such as steel, stainless
steel, which may have been surface-treated, e.g. phosphatized or
galvanized. The metal substrate may also be iron, aluminum, copper, brass,
bronze, nickel, zinc and their alloys. A preferred substrate is steel
which has the substrate surface grit blasted. Another preferred substrate
is steel which has a phosphate conversion layer or coating (i.e.,
phosphate-based corrosion inhibitor coatings, phosphatized). These
phosphate coatings can be organic or inorganic. Phenolic and other organic
primers can be used but are not necessary for adhesion. The adhesive will
also bond two or more metal substrates.
Some nonmetallic materials, such as molding compositions comprising
phenolic resin or polyester resin and/or urethanes which may include woven
fabrics, nonwoven, or chopped fiber of natural or synthetic origin (e.g.
glass) may be adhered.
The adhesive compositions of the present invention may be prepared by any
method known in the art, but are preferably prepared by combining and
milling the ingredients and water in a ball-mill, sand-mill, ceramic
bead-mill, steel bead-mill, high speed media-mill, or the like.
The bonding composition in accordance with the invention desirably contains
between 12 and 50 percent by weight solids and desirably has a viscosity
of about 10 to 1000 centipoise (Pa.s) for ease of application and can be
applied to the substrate or rubber surfaces by conventional methods, such
as brushing, spraying, rollcoated and dipping. One or more surface areas
of the metal substrate and/or rubber which are going to be bonded by the
adhesive are the interfacial bond areas. One substrate surface (either
metal or rubber), or optionally both, are covered by an adhesive layer.
Multiple coatings or layers may be used. After the coating has been
applied and the water at least partially evaporated, the surfaces of the
interfacial bond areas of the substrates are contacted with each other and
the bond is formed under vulcanizing conditions which includes the
application of heat to at least the adhesive layer and may include the
application of pressure. The temperature activating the cure of the
adhesive is desirably from about 120.degree. C. to about 200.degree. C.
and more desirably from about 140.degree. C. to about 180.degree. C.
Depending on the temperature the bond is desirably formed in from about 3
to about 60 minutes.
The advantages afforded by the adhesive composition in accordance with the
invention are that it can be prepared in a simple manner, has a long
shelf-life, and does not require an organic primer layer on the metal
substrate. The lack of a primer saves time. The adhesive has a universal
utility for bonding of rubbers to metals or metals to metals or rubbers to
rubbers. It can be used with specialty types of rubber and various
substrate materials. The resulting bond has a high resistance to
corrosion, to elevated temperatures, and to boiling water and glycols.
Being water-based, it has low or near zero volatile organic emissions
during drying (desirably less than 1.0, 0.5, 0.1, or 0.05 wt. % volatile
organics as defined above for organic solvents in said adhesive
composition). The laminates are useful as components in vehicle vibration
control products that have elastomer to metal interfaces.
1. Substrates
In the following examples the rubber compound of Table IX is a formulation
suitable for use in automotive engine mount applications. It is cured for
about 10 minutes at 160.degree. C. Typically after curing it has a Shore A
hardness of 58. The metal substrates were cold rolled steel coupons
(1".times.2.5" equiv. to 2.5.times.6.4" cm) treated with calcium modified
zinc phosphate coating.
2. Latexes
The ethylene oxide macromonomer was first prepared in Example 1. In Example
2 a latex that was prepared was subsequently used as a seed latex in
forming latexes of Examples 3-6. The latex of Example 7 was formed without
a seed latex.
3. Adhesive Composition
The adhesives are aqueous dispersions of a copolymer of butadiene and
vinylidene chloride, an effective amount of aromatic polynitroso compound,
an effective amount of coactivator, zinc oxide and fillers. The adhesive
compositions of Tables X-XIII contain the latexes of Tables III-VII.
Zinc oxide may participate in ionic bond formation with the carboxylic
groups of the latex. The resulting ionic domains may enhance mechanical
strength.
To form a more stable dispersion, the water-based adhesive contains an
anionic dispersant, Polywet.TM. Z1766 (sodium salt of a polyfunctional
oligomer, supplied by Uniroyal Chemical Co.), and a nonionic dispersing
agent, Natrosol.RTM. 250LR (hydroxyethyl cellulose supplied by Aqualon
Corp.).
Preparation of the Adhesive
a. Deionized water (220 g) was placed in ball mill jar, followed by
Natrosol.TM. 250LR (2.0 g), Polywet.TM. Z1766 (2.0 g), Benzoquinone (0.2
g) and HVA-2 (1,1'-(methylene-di-4,1-phenylene) bismaleimide, supplied by
DuPont Chemical Co.) (9.2 g).
b. Aqueous dispersions of 37.5 g. AquaBlack.RTM. (40 weight percent), 17 g
Zeeox.RTM. (50 percent zinc oxide in water) and 51 g PDNB (poly
(para-dinitrobenzene) 50 percent paste in water supplied by MLPC
International) were added to the materials of above. The ball mill jar was
rotated for 5 hours. The resulting dispersion was a finely divided black
dispersion, designated as the curative masterbatch.
c. A 36 g aliquot of the curative masterbatch was added to a clean
container with a stirring bar, then 7.4 g dry basis of a latex of Tables
III-VII was slowly added while stirring. The final adhesive composition
contains 25 weight percent solids and 75 weight percent water.
4. Applying the Adhesive
Because the adhesive contains dispersed solids in water, it is necessary to
adequately agitate the mixture prior to use. The adhesive compositions
were applied to phosphated metals by brush, an air gun, or an airless
spray gun. To decrease drying time, the metals may be preheated to
60.degree. C. Dried film thicknesses were from 0.5 mil to 1 mil (0.013 to
0.025 mm).
5. Curing of Rubber and Adhesive
The metals coated with the adhesives and uncured NR substrate of Table I
are brought together and compression molded at 20,000 lbs. (44,000 kg) ram
force spread over six test specimens of dimensions 1".times.2.5"
(2.5.times.6.4 cm) and heated for 10 minutes at 160.degree. C.
6. Testing
Adhesion testing was carried out at room temperature with an Instron
Tester. Compression molded rubber-to-metal parts were peeled at a rate of
2 inches/minute at a 90.degree. peel angle, according to ASTM D429, Method
B for uncured rubber. The maximum peel force and the percent rubber
retained on a one square inch surface were recorded as the mean of three
specimen per sample.
EXAMPLE 1
Liquid monohydroxyl-end functionalized ethoxylated materials from
Rhone-Poulenc (Igepal.RTM.) (alkylphenoxypoly(ethylenoxy)ethanol) were
reacted with m-isopropenyl-.alpha.,.alpha.-dimethyl benzyl isocyanate
(TMI.RTM. Cytec) in the presence of a stannous octoate catalyst at a
temperature of 65.degree. to 100.degree. C. The amount of hydroxyl groups
of the ethoxylated polymeric species was kept in excess of the isocyanate
groups (approximate stoichiometry of 111 to 105%) and the extent of the
reaction was monitored by infrared (IR) spectroscopy. When IR spectroscopy
indicated no free isocyanate was present, the samples were poured into a
container for storage. The resulting macromonomer is terminated at one end
with an .alpha.-methylstyrene functional group. The carbon-carbon double
bond of this macromonomer is amenable to free radical emulsion
polymerization. The other end of the macromonomer is either an
octylphenoxy or nonylphenoxy group.
TABLE I
______________________________________
Wt. %
Macro- Ethylene Oxide
Ethylene Oxide
Pretreatment of
monomer Designation
in Igepal Ethylene Oxide
______________________________________
1-A Igepal CA 210
23 used as received
1-B Igepal CA 520
44 used as received
1-C Igepal CO 897
89 dried at reduced pressure
1-D Igepal CA 881
86 dried at reduced pressure
1-E Igepal CA 630
65 used as received
______________________________________
CA denotes octylphenoxypoly(ethyleneoxy)ethanol
CO denotes nonylphenoxypoly(ethyleneoxy)ethanol
EXAMPLE 2
In this example a seed latex is prepared in two steps from styrene and
itaconic acid for use in subsequent latex formulations. The reaction went
essential to 100% conversion without any coagulum. The amount of water
used is not listed but as seen in the solids determination it is about 91
wt. % of the latex. PPHM is parts by weight per one hundred parts of
polymerizable monomers in the recipe.
TABLE II
______________________________________
PREPARATION OF SEED LATEX
Components PPHM
______________________________________
Step 1: (2 hours at 65.degree. C.)
Itaconic Acid 30.1
Hampene .TM. Na3T 1.0
Dowfax .TM. 2A1 2.8
Monawet .TM. MB-45 20.1
Styrene 69.9
Ammonium Persulfate
6.0
Solids (%) 9.1
Step 2: (1 hour at 63.degree. C.)
Disodium Phosphate 4.0
Solids (%) 8.8
______________________________________
*Dowtax .TM. 2A1 is sodium diphenyloxide sulfonate (15% active)
Monowet .TM. MB45 is dibutyl sodium sulfosuccinate (45% active)
Hampene .TM. Na3T is ethylenediaminetetraacetic acid, trisodium salt
trihydrate (40% active) a sequestering agent.
EXAMPLE 3
Preparation of Latexes with and without Unfunctionalized Iqepal CA 210 or
CA 520
Butadiene-vinylidene chloride latexes were prepared having high conversion
of monomers to polymer and low coagulum levels using the latex of Example
2 as a seed. The polymerizations were performed in two steps. The first
step was polymerization for approximately 22 hours at 65.degree. C. The
second step was further polymerization to the point of reduced pressure
(i.e. vacuum). The latexes were cooled and their properties determined.
These latexes serve as control material.
TABLE III
______________________________________
Control
Latexes 3-A 3-B 3-C 3-D 3-E 3-F
______________________________________
Step 1:
Seed Latex
6.8 g* 6.8 g* 6.8 g*
6.8 g*
6.8 g*
6.8 g*
Example 2
Igepal .TM.
1.2 2.5 0 0 0 0
CA 210
Igepal .TM.
0 0 0 1.2 2.5 4.2
CA 520
Vinylidene
10.0 10.0 10.0 10.0 10.0 10.0
Chloride
Sulfole 120
1.6 1.6 1.6 1.6 1.6 1.6
Ammonium 0.3 0.3 0.3 0.3 0.3 0.3
Persulfate
Butadiene
90.1 90.1 90.1 90.1 90.1 90.1
Step 2:
Ammonium 0.3 0.3 0.3 0.3 0.3 0.3
Persulfate
Total Solids
37.0 37.1 36.4 33.2 36.7 37.1
Content (%)
______________________________________
*Dry basis
Sulfole 120 is tertiary dodecyl mercaptan (a chain transfer agent).
EXAMPLE 4
Polymerization of Latexes with Functionalized Igepal CA 210 or CA 520
Latexes from butadiene-vinylidene chloride and a macromonomer were
polymerized using the latex of Example 2 as a seed and the macromonomers
1A or 1B (derived from Igepal CA 210 or CA 520 respectively). The
reactions were performed in two steps as previously outlined.
TABLE IV
______________________________________
Latexes 4-A 4-B 4-C 4-D 4-E
______________________________________
Step 1:
Seed Latex Example 2
6.8 *g 6.8 *g 6.8 *g
6.8 *g
6.8 *g
Macromonomer 1-A
1.2 2.5 0 0 0
Macromanomer 1-B
0 0 1.2 2.5 4.2
Vinylidene Chloride
10.0 10.0 10.0 10.0 10.0
Sulfole 120 1.6 1.6 1.6 1.6 1.6
Ammonium Persulfate
0.3 0.3 0.3 0.3 0.3
Butadiene 90.1 90.1 90.1 90.1 90.1
Step 2:
Animonium Persulfate
0.3 0.3 0.3 0.3 0.3
Total Solids Content (%)
37.2 37.5 37.3 37.4 37.9
______________________________________
*Dry basis
EXAMPLE 5
Polymerization of Latexes with a Blend of Functionalized Iqepal CA 210 and
Functionalized CA 520
A latex from butadiene-vinylidene chloride and a blend of macromonomers was
polymerized as previously outlined using Example 2 as a seed latex. A
blend of macromonomers (1-A and 1-B) from Igepal CA 210 and Igepal CA 520
from Example 1 was used.
TABLE V
______________________________________
Latex 5A
______________________________________
Step 1:
Latex Example 2 6.8 *g
Macromonomer 1-A 1.2
Macromonomer 1-B 1.2
Vinylidene chloride
10.0
Sulfole 120 1.6
Ammonium Persulfate
0.3
Butadiene 90.1
Step 2:
Ammonium Persulfate
0.3
Total Solids Content (%)
37.6
______________________________________
*Dry Basis
EXAMPLE 6
Polymerization of Latexes with Functionalized Igepal CA 881 or Igepal CA
630
Butadiene-vinylidene chloride latexes as were prepared as outlined above
using macromonomers 1-D and 1-E as prepared in Example 1 from Igepal CA
881 or CA 630 respectively.
TABLE VI
______________________________________
Latexes 6A 6B
______________________________________
Step 1:
Latex Example 2 6.8 *g 6.8 *g
Macromonomer 1-D 2.5 0.0
Macromonomer 1-E 0.0 2.5
Vinylidene Chloride
10.0 10.0
Sulfole 120 1.6 1.6
Ammonium Persulfate
0.3 0.3
Butadiene 90.1 90.1
Step 2:
Ammonium Persulfate
0.3 0.3
Total Solids Content (%)
33.4 37.3
______________________________________
*Dry Basis
EXAMPLE 7
Polymerization of Latex with Functionalized Igepal CO 897 and without a
Seed
A butadiene-vinylidene chloride latex was polymerized to high conversion
and low coagulum level without any seed using macromonomer 1-C from Igepal
CO 897. The reaction was performed in two steps. The first step was run
for approximately 22 hours at 65.degree. C. The second step was then run
to the point of reduced pressure (i.e. vacuum). The latex was cooled and
its properties determined.
TABLE VII
______________________________________
Latex 7A
______________________________________
Step 1:
Macromonomer 1-C 2.5 g
Vinylidene Chloride
10.0
Sulfole 120 1.6
Ammonium Persulfate
0.3
Butadiene 90.1
Step 2:
Ammonium Persulfate
0.3
Coagulum (%) 0.6
Total Solids Content (%)
37.6
______________________________________
EXAMPLE 8
Adhesive Preparation
Adhesives were prepared using the formulation given below. The latex
denotes the latexes from Examples 3 to 7. The final solids content is
about 25 wt. %.
TABLE VIII
__________________________________________________________________________
ADHESIVE FORMULATION
Formulation Wt %
Component Dry Basis
Description
Supplier
__________________________________________________________________________
Natrosol 250LR
1.5 hydroxyethyl cellulose
Aqualon Corp.
Benzoquinone
0.2
Polywet Z-1766
1.5 sodium salt of a
Uniroyal Chemical Co.
polyfunctional oligomer
Phenylene bis-maleimide
7.0
Poly p-Dinitroso Benzene
19.3 50% paste in water
MLPC International
Aqua Black 11.4 40% dispersion in water
Bordon Packaging and
Industrial Products
Zinc Oxide 6.4 50% dispersion in water
Zee Chem Inc.
Latex (dry) 52.7
__________________________________________________________________________
% Solids of Adhesive: 25%
EXAMPLE 9
TABLE IX
______________________________________
NATURAL RUBBER FORMULATION
Material phr
______________________________________
Natural Rubber, SMR-GP 100.0
Carbon Black, N550 42.0
Carbon Black, N990 10.0
Naphthenic Oil 6.0
Zinc Oxide 5.0
Stearic Acid 2.0
Santoflex .TM. 13 N-1,3-Dimethylbutyl-
0.5
N'-phenyl-p-phenylenediamine
PVI N-(cyclohexylthio)phthalamide
0.2
MBT .TM. 2-mercaptobenzothiazole
0.3
MBTS .TM. Benzothiazyl disulfide
0.3
CBS .TM. N-cyclohexyl-2-benzothiazyl-sulfenamide
0.4
Sulfur 3.0
______________________________________
EXAMPLE 10
Comparison of Freshly Prepared Laminated Samples
This example illustrates the superior performance of latex including the
macromonomer from Igepal CA 210 therein (Latexes 4A and 4B) in the
adhesive when compared to those of the corresponding latexes with
unfunctionalized versions of Igepal CA 210 (Control Latexes 3-A and 3-B)
or without any macromonomers (Control Latex 3C).
This example also illustrates the superior performance of a latex using the
macromonomer from Igepal CA 520 (Latexes 4C, 4D, and 4E) when compared to
the material without a macromonomer (Control Latex 3C) and those
containing the unfunctionalized version of Igepal CA 520 (Control Latexes
3D, 3E and 3F).
TABLE X
______________________________________
ADHESION (90.degree. T-PEEL) OF CURED
NATURAL RUBBER TO SAND BLASTED STEEL
Max. Load Rubber Tear*
Latex kg/cm and (pli)
(%)
______________________________________
Control 3-A (CA 210)
12.1 (68) 20
Control 3-B (CA 210)
4.8 (27) 10
Control 3-C 4.5 (25) 10
Control 3-D (CA 520)
10.7 (60) 20
Control 3-E (CA 520)
7.3 (41) 23
Control 3-F (CA 520)
13.9 (78) 70
(CA 210) 19.6 (110) 90
(CA 210) 23.0 (129) 100
(CA 520) 20.2 (113) 90
(CA 520) 22.5 (126) 100
(CA 520) 16.1 (90) 60
______________________________________
*High amounts of rubber tear indicate the adhesive is stronger than the
rubber substrate.
EXAMPLE 11
Comparison of the Performance after Aging
This example illustrates the superior long-term performance of the water
based adhesives containing macromonomer modified latexes (Latexes 4C and
4E) using a macromonomer from Igepal CA 520 when compared to adhesives
from latexes with the corresponding unfunctionalized version of Igepal CA
520 (Latexes 3D and 3F).
TABLE XI
______________________________________
ADHESION (90.degree. T-PEEL) OF CURED
NATURAL RUBBER TO SAND BLASTED STEEL
Max.
Load Rubber
kg/cm and Tear Days
Latex (pli) (%) Aged
______________________________________
4-C Macromonomer 1B
20.2 (113) 90 0
17.7 (99) 90 6
4-E Macromonomer 1B
16.1 (90) 60 0
20.9 (117) 100 1
17.1 (96) 100 7
14.6 (82) 90 10
(Control) 3-D 10.7 (60) 20 0
13.9 (78) 50 7
(Control) 3-F 13.9 (78) 70 0
7.5 (42) 10 6
10.9 (61) 50 11
______________________________________
EXAMPLE 12
Comparison of the Bond Strength for a Latex with Mixed Functionalized
Igepal Macromonomers
This example illustrates the performance of latex containing mixed
macromonomers (Latex 5A) using macromonomers from Igepal CA 210 and CA
520. The resulting adhesive was superior to the adhesive containing no
macromonomer (Latex 3C).
TABLE XII
______________________________________
ADHESION (90.degree. T-PEEL) OF CURED
NATURAL RUBBER TO SAND BLASTED STEEL
Max. Load Rubber Tear
Latex kg/cm and (pli)
(%)
______________________________________
5A 16.4 (92) 90
(Control) 3C 4.5 (25) 10
______________________________________
EXAMPLE 13
Bonding of Uncured Rubber to Zinc Phosphated Steel
This example illustrates the performance of a latex containing a
macromonomer (Example 6B using a macromonomer from Igepal CA 630) for
bonding natural rubber to zinc phosphated steel.
TABLE XIII
______________________________________
Max. Load Rubber Tear
Latex kg/cm and (pli)
(%)
______________________________________
6-C 19.6 (110) 95
______________________________________
While in accordance with the patent statutes the best mode and preferred
embodiment has been set forth, the scope of the invention is not limited
thereto, but rather by the scope of the attached claims.
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